Hello again!
As I remember on good old DOpus 4 on Amiga it was possible, to open (NOT copy/move) a folder into the other lister (Dual View) via drag'n'drop (or click'n'click!).
Is there such an option in DOpus (I don't find it)?
Ctrl - Dbl Click LMB will open the folder in the destination pane by default I think.
You can configure this behaviour in Settings / Filetypes.... Edit the 'All Folders' filetype and go to the events tab.
Great, thank you for the tip (shift dbl). I will try configure this without pressing keyboard.
A last question: Where can I change the context menü that is shown with rmouse drag'n'drop?
In the filetype editor there's a drop menu tab next to the events tab which should be what you're after.
By the way, you can also create a toolbar button to do this, using the same command as you'll find in the event.
I like to move it to the middle-double-click event so I can trigger it without the keyboard.
Thank you for the good and fast help.
I've read the manual the last few days, but I can't remember & try everything - it's simply too much 
Take your time learning everything and let your configuration evolve over time. Mine certainly is, even after several years, as I keep thinking of new things to save time or I need to do new jobs or take advantage of new features.
[quote="Sasa"]Thank you for the good and fast help.
I've read the manual the last few days, but I can't remember & try everything - it's simply too much [/quote]
You can only eat an elephant one bite at a time. I must add at least one new customization to my Opus configuration each week. We are all learning here, we have just all started at different times, and in different areas of Opus.